Notify OverscrollController of gesture events in plugins.

content/browser/renderer_host/render_widget_host_view_base.h

Index: content/browser/renderer_host/render_widget_host_view_base.h
diff --git a/content/browser/renderer_host/render_widget_host_view_base.h b/content/browser/renderer_host/render_widget_host_view_base.h
index 712270847066af3c7dc89d3d85a2e348fc550f32..2c81630590e994244623c2d2470fe6bd3b795891 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.h
+++ b/content/browser/renderer_host/render_widget_host_view_base.h
@@ -187,6 +187,10 @@ class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
   virtual InputEventAckState FilterInputEvent(
       const blink::WebInputEvent& input_event);
 
+  // Allows a root RWHV to filter gesture events in a child.
+  virtual InputEventAckState FilterChildGestureEvent(
+      const blink::WebGestureEvent& gesture_event);
+
   // Called by the host when it requires an input flush; the flush call should
   // by synchronized with BeginFrame.
   virtual void OnSetNeedsFlushInput() = 0;